How much a theory of law can tell us about the nature of morality: a response to Mark Greenberg's How facts make law

Abstract

In his outstanding paper "How Facts Make Law," Mark Greenberg argues for the antipositivist claim that descriptive facts about certain social practices are not the only necessary determinants of legal content; "value facts" - which he is committed to construing as moral facts - are another necessary determinant of legal content. In this essay, I argue that, construed as doing the work Greenberg believes it does in refuting positivism, his conclusion that legal content is not possible without value facts has certain implications about the nature of morality that no purely metaphysical considerations about the relationship between social practices and the content of social norms can plausibly have. In particular, Greenberg's conclusion, together with the obvious (because extremely weak) truth that law is possible, seems to imply moral objectivism - a highly contested view in general ethical theorizing. I take this to be a reductio of his view, as it seems clear that no theory relying on general metaphysical claims about social practices can bear such weight.